ST Disk Converter

ST Disk Converter turns Atari ST floppy disk images (or folder) between MSA and ST on your Mac.

MSA is the Magic Shadow Archiver format used to store Atari ST disks. ST is the plain disk image used by MiSTer and other Atari ST emulators. Drop either kind of file and ST Disk Converter writes the other.

Drop a disk Drop one .msa or .st file onto the window, or click the well to choose it. You can also drop several files at once. A folder is scanned for every disk image inside it, including images in nested folders.

MSA to ST An MSA file is decoded track by track. Compressed tracks are expanded, and the result is a raw .st disk image. The window shows how many sides the disk has, its track range, sectors per track, and the size of the converted file.

ST to MSA An ST file is packed back into MSA using the same track format. Usual Atari floppy sizes are recognised, including 360 KB, 720 KB, and 800 KB disks.

Save Save a single converted file, or choose a destination folder when several disks were converted. Files found in subfolders keep that folder structure, with each image saved in the opposite format.

ST Disk Converter was ported to macOS by TikiDays Software. Conversion is based on msa-to-st-converter by Markus Velten and others, released under the MIT License.

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